Re: VIRTIO_BLK_T_SCSI_CMD handling in virtio-blk

[Christian Borntraeger]

Am Wednesday 18 March 2009 07:09:19 schrieb Christoph Hellwig:
> Currently virtio-blk just sends down the payload for packet command
> requests, setting the VIRTIO_BLK_T_SCSI_CMD flag in the type field and
> zeroing out the sector field.
> 
> But to make any sense of the payload of a packet command we need the
> scsi command block (request->cmd) which specifies the operation,
> location and length for this command.
> 
> All backends that I checked just fail VIRTIO_BLK_T_SCSI_CMD commands, so
> AFAICS no harm is done.  But should we really keep this broken support
> in the protocol around?  If we do want to support packet commands in
> the future we should probably just add the command as the first S/G list
> entry.

Hannes did some implementation for SCSI command passthrough:
https://lists.linux-foundation.org/pipermail/virtualization/2008-August/011629.html

After some addon fix this was working pretty well. I dont know why Hannes never
pushed the final version upstream.

Christian
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